1. Field of the Invention
The present invention relates to vibration damping in a hard disk drive device, and more particularly to a vibration damped flexible circuit for use in such a disk drive device.
2. Description of the Related Art
Moving magnetic storage devices, especially magnetic disk drives, are in prevalent use in computer systems, due in large part to their ability to inexpensively store large quantities of non-volatile data for quick access. Magnetic disk drives utilize at least one rotatable magnetic media disk having concentric data tracks defined for storing data, a magnetic recording head or transducer for reading data from and/or writing data to the various data tracks, a slider for supporting the transducer in close proximity to the data tracks typically in a flying mode above the storage media, a suspension assembly for resiliently supporting the slider and the transducer over the data tracks, and a positioning actuator coupled to the transducer/slider/suspension combination for moving the transducer across the media to the desired data track and maintaining the transducer over the data track center line during a read or write operation. The transducer is attached to or is formed integrally with the slider which supports the transducer above the data surface of the storage disk by a cushion of air, referred to as an air-bearing, generated by the rotating disk.
Alternatively, the transducer may operate in contact with the surface of the disk. Thus, the suspension provides desired slider loading and dimensional stability between the slider and an actuator arm which couples the transducer/slider suspension assembly to the actuator. The actuator positions the transducer over the correct track according to the data desired for a read operation or to the correct track for placement of the data during a write operation. The actuator is controlled to position the transducer over the desired data track by moving the transducer across the surface of the disk in a direction generally transverse to the data tracks. The actuator may include a single arm extending from a pivot point, or alternatively a plurality of arms arranged in a comb-like fashion extending from a pivot point. A rotary voice coil motor (VCM) is attached to the rear portion of the actuator arm or arms to power movement of the actuator over the disks. The term seek refers generally to the radial movement of the head or transducer to a specified track on the disk.
The VCM located at the rear portion of the actuator arm is comprised of a top plate spaced above a bottom plate with a magnet or pair of magnets therebetween. The VCM further includes an electrically conductive coil disposed within the rearward extension of the actuator arm and between the top and bottom plates, while overlying the magnet in a plane parallel to the magnet. In operation, current passes through the coil and interacts with the magnetic field of the magnet so as to rotate the actuator arm around its pivot and thus position the transducer as desired.
The magnetic media disk or disks in the disk drive are mounted to a spindle. The spindle is attached to a spindle motor, which rotates the spindle and the disks to provide read/write access to the various portions on the concentric tracks on the disks. One or more electrical conductors extend over the suspension assembly to electrically connect the read/write transducer to a read/write chip on the actuator arm. A multi-line flexible printed circuit cable (actuator flex cable) provides the electrical contact between the read/write chip and other circuitry located outside the disk drive housing. Inside the disk drive housing, the actuator flex cable connects to an electrical connector pin assembly, which in turn, through an opening or connector port in the housing, connects to the external electronics.
The actuator flex cable is a flexible circuit that carries electrical signal to and from the actuator. It is typically comprised of a plurality of electrical conductors encapsulated within an insulating material. The actuator flex cable provides electrical contact from the external electronics fixed to the disk drive housing to the actuator which is supported on bearings allowing radial motion of the actuator about its pivot point. The radial motion of the actuator allows the read/write transducers supported on suspensions fixed to the actuator to access data tracks on the disk surfaces located at any radial position from the inside diameter of the disk to the outside diameter of the disk. The preferred method of fixing the actuator flex cable between the electronics card on the fixed disk drive housing and the rotatable actuator is to form the actuator flex cable in a loop so that the actuator flex cable causes minimal constraint on the actuator rotation. The loop of the actuator flex cable connecting the actuator with the electronics card can vibrate during seeking of the actuator, introducing unwanted vibration modes to the actuator. Vibration (often referred to as random transient vibration) of the actuator during seek operations degrades settling performance of the disk drive.
There have been attempts in the prior art to minimize the affects of flex cable vibration on the actuator or head carriage assembly positioning. For example, U.S. Pat. No. 5,907,452 issued to Kan discloses attaching a damper at one end of the flex cable, the damper being a component external to and separate from the flex cable. Those skilled in the art will appreciate that the additional components added by the prior art necessarily increase the cost and complexity of such device, and in some cases increase the risk that the added components may become dislodged resulting in a catastrophic failure of the disk drive. In addition such a device only provides damping to a portion of the flex cable. Therefore, there remains a need for a means for effectively damping vibration in a flexible cable of a disk drive device, while minimizing the use of addition components. Such a device would preferably make use of existing manufacturing techniques as much as possible.